1. Field of the Invention
The present invention relates to a coupling device for a force transmitting member, and more particularly to such a coupling device in which a hardened cement composition is being filled.
2. Related Art Statement
In the conventional technology for transmitting force through a tension member or a compression member (these members being inclusively referred to as "force transmitting member" in the following description), there has been widely employed a method or measure wherein a joint is used to connect the force transmitting members. For example, iron or steel rods each having threaded ends are connected by a coupler having threaded holes, or fiber reinforced plastic rods each having a recess or projection are connected by a coupler having projections or recesses engaging with the recesses or projections of the rods. However, since some clearance is needed for engaging operation, it is inevitable that trembling or jolting occurs after the force transmitting members are connected by such joint means. Not only such trembling or jolting is detrimental in connecting a precise mechanism, but also the trembling or jolting causes fissure or cracking of a material having small tensile stress of elasticity such as concrete if such a material is present in the vicinity of the force transmitting members. Although it has been proposed to fill in a gap between the joint and the force trasmitting member with a resinous material, such as an epoxy resin, in order to prevent trembling, such a resinous material has various disadvantages in that it has high hydrate contraction, a low compressive modulus of elasticity and a high creep after being hardened and that it is low in heat resistance and in durability. On the other hand, it has been tried to use the conventional cement composition as the filler for filling in such a gap. However, the compressive strength of the conventional cement composition is small, and the compressive modulus of elasticity and the strength thereof are inevitably low since water content has to be increased to improve the fluidity for filling in a very small gap (clearance) in-between the force transmitting member and the joint.
If a material having low compressive modulus of elasticity and low strength is filled in the clearance, when a force is applied on the force transmitting member, the filler is dislocated for the lack of compressive modulus of elasticity to thereby cause undesirable shift of the position of the force transmitting member or the filler is crushed due to insufficient compressive strength so as not to fulfill its service as the filler. It was thus impossible to prevent the joint from trembling or jolting by the use of the known fillers.